The design and the miniaturization of cameras continue to present many issues. For example, the ability of a system to provide good images at low light levels has been sought for many years.
U.S. Pat. No. 3,971,065 discloses a color imaging array having a single sensor. The patent discloses a RGGB filter over the pixel. This provides high luminance resolution and also good sensitivity. However, using this technique, more light reaches the white pixel (as compared with the RGB pixels), which means that the RGB pixels are underexposed and thus suffer from noise issues.
U.S. Pat. No. 7,199,348 discloses an apparatus for multiple camera devices and method of operating the same, which discloses using separate sensors at different wavelengths and different integration times. There is no teaching of how the sensors can be aligned or how multiple sensors can be used to assist in low light conditions.
A technique known as white light illumination has a standard color image sensor and white light illumination such as a flash or LED. A flash is power efficient but not suitable for video applications, and white light is not very efficient for portable applications were energy storage is critical. In addition, bright light can prove a distraction to the subject thereby making filming unpleasant.
A thicker epitaxial Silicon layer is known to alter the absorption depth of light in Silicon in a wavelength dependant manner, with longer wavelengths penetrating deeper into the Silicon. This can be used to adapt a device for different wavelengths but has certain disadvantages associated therewith.
While the prior art addresses some issues, a camera module which can adequately deal with low light levels is still needed.